Patent Document 1 discloses the configuration of a solid polymer fuel cell (hereinafter, abbreviated to fuel cell). In the fuel cell disclosed in Patent Document 1, a membrane electrode assembly includes an electrolyte film made of a solid polymeric membrane and two electrode catalytic layers. The electrode catalytic layers are respectively connected to the two surfaces of the electrolyte film. The membrane electrode assembly is held between two separators to form a cell. A fuel cell is then formed by laminating cells.
The separators of the fuel cell disclosed in Patent Document 1 include a base portion, which is formed of aluminum or steel sheet, and a coat layer, which is formed of titanium nitride and coats the base portion. In forming the coat layer on a surface of the base portion, a film forming technique such as physical vapor deposition (PVD) or chemical vapor deposition (CVD) is used.